A path towards a compact, CW FEL using superconducting rf accelerator technology

Recently, several compact FELs have been built based on pulsed linacs and RF photocathode guns. There is now an exciting opportunity to extend the capability of the technique to CW operation by incorporating the recent development in superconducting electron accelerators. The higher average power possible with CW operation will enhance the utility and the versatility of the compact FELs for fundamental research as well as for industrial application. Our vision of an eventual compact high power FEL is one that is targeted to have a foot print of 1 × 6m2. It would consist of a CW RF superconducting photocathode gun closely coupled to a superconducting accelerator cavity, all in a single cryostat, producing a 6–15 MeV beam. The helium refrigerator will be built into the compact dewar as is currently being done for the JAERI FEL in Japan. The FEL output will consist of 10–100 μJ pulses at 10–70 MHz repetition rate with average power greater than 1 kW. The FEL performance will be optimized in the wavelength range between 10 and 50 μm, which is a difficult region for conventional laser techniques. Longer wavelengths can be generated via Cherenkov FEL, and X-rays can be produced via Thomson scattering.